The game has got a more convenient way to buy crystals now. Now you can purchase them in packages. Choose one of five packages each of which contains a bonus in the form of free crystals. The larger the package, the bigger the bonus! For example, when purchasing 5,000 crystals you get 1,000 as a bonus. If you buy 15,000 crystals, you get 5,000 for free. You can find more information in the forum.